1. Field of the Invention
The invention is a composite bicycle frame combining a metal spine with a fiber reinforced plastic composite seat tube, top tube, seat lug and seat stay assembly.
2. Description of Related Art
Bicycle frames formed as composites, namely comprising different materials, have been long known. These date back to historical times using wood with metal joints or reinforcements. In modern times, steel frames using investment cast lugs or joints and drawn or extruded tubes are well-known. More recently, a combination of metal lugs and fiber reinforced plastic composite tubes, particularly carbon fiber reinforcing an epoxy matrix, have been known. An example is U.S. Pat. No. 4,900,049 issued to Tseng which illustrates investment cast aluminum lugs, taught they are primarily for use with aluminum tubes, but which could also use carbon fiber tubes. Other carbon fiber frames include U.S. Pat. No. 4,047,731 issued to Van Auken and U.S. Pat. No. 4,493,749 issued to Brezina.
More recently, bicycles in which the main triangle is formed of a high strength, light weight metal, such as titanium and the rear triangle, more specifically the seat stay assembly and chain stays, have been made of carbon fiber tubes. Typically, the rear dropouts have been metal in all cases because of reater durability when subject to the clamping of the wheels to the frame. It is also believed that a company called Merlin has used carbon top tube, seat tube, and monostay but have joined all together with a welded titanium seat cluster.